A common method of moving parts or components along a manufacturing assembly line is by means of overhead conveyors. Such conveyors may be formed of a number of wheeled trolleys which ride along a guideway or track in a continuous closed loop. The trolleys are connected by a conveyor chain formed of a number of connected links, and the parts or components are suspended from the trolley.
The conveyor chain is typically driven by a motorized sprocket assembly which provides force for powering the wheeled trolleys along the guideway or track. Although the wheeled trolleys and the parts or components suspended from the trolley have their weight supported by the guideway or track, the conveyor chain is still subjected to wear over an extended period of time. These conveyor chains may be very lengthy as they may travel and extend throughout a large production facility. Thus, such conveyor chains may be subjected to numerous random forces and stress as well as a variety of environmental conditions such as heat fluctuations, oils, solvents and other caustic solutions.
Due to the above-noted conditions, the wear of the conveyor chain should be monitored in order to prevent a conveyor chain from breaking or possibly damaging other components of the conveyor system. One of the most closely watched chain wear parameters is chain stretch which is defined as the linear distance in which the chain lengthens over a period of time due to wear. Chain stretch often occurs through the eventual wearing of the conveyor chain's pivot pins which are utilized to connect successive links of the chain. The movement of the pivot pins within the apertures of the links eventually wear and create "slop". This "slop" along with yielding of the links, will essentially make the conveyor chain longer when pulled taught.
Minor wear or chain stretch is allowable and expected within the industry, but when chain stretch becomes excessive, it may cause numerous problems. For one, the sprocket may not be able to properly engage the conveyor chain should the chain stretch become excessive enough that the teeth of the sprocket skip a space between links or apply forces to a link that may bend or damage the conveyor chain. Also, extensive chain stretch may cause the conveyor chain to sag thus affecting the smooth travel of the wheeled trolleys along the guideway or track. Yet, the greatest concern is that excessive chain stretch may lead to the eventual thinning and breaking of the conveyor chain.
In order to monitor the chain stretch of a conveyor chain, a certain length of the conveyor chain is often measured manually to ensure that the chain stretch does not exceed a predetermined value. It is well known and common in the art to monitor and measure ten foot sections of the conveyor chain. The problem with making such manual measurements is that the conveyor chain must be stopped in order to make a proper measurement. This requires that the entire conveyor be shut down which prevents and delays the parts or components delivered by the conveyor from being supplied to the assembly or production line. Obviously, this creates an inefficiency that is undesirable in a production environment.
In addition, manual measurements of chain stretch typically have the problem of being inaccurate as they are conducted with tape measures which can hardly be considered accurate for repetitive measurements of ten foot chain lengths. Also, the ten foot section of conveyor chain selected for measurement is typically random, and therefore, no recorded history exist or is maintained as to the wear of that particular section of conveyor chain. This becomes an even greater disadvantage when a portion of the chain has been replaced by either a different manufacturer or different material, and thus, an evaluation as to the performance and wear of the individual sections of the conveyor chain cannot be made. In addition, manual chain wear measurements rely on an operator to continually measure the conveyor chain. Should the operator fail to continually monitor the chain, any number of the above-noted results can occur.